Phosphorescent phosphor

ABSTRACT

PCT No. PCT/JP96/02149 Sec. 371 Date Jul. 20, 1998 Sec. 102(e) Date Jul. 20, 1998 PCT Filed Jul. 30, 1996 PCT Pub. No. WO97/27267 PCT Pub. Date Jul. 31, 1997A phosphorescent phosphor represented by m(Sr1-a,M1a)O.n(Mg1-b, M2b)O.2(Si1-c,Gec)O2:EuxLny, wherein M1 is Ca and/or Ba, M2 Be, Zn and/or Cd, Ln is Sc, Y, La, Ce, Pr, Nd, Sm, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, B, Al, Ga, In, Tl, Sb, Bi, As, P, Sn, Pb, Ti, Zr, Hf, V, Nb, Ta, Mo, W, Cr and/or Mn, and wherein a, b, c, m, n, x and y are within ranges of 0&lt;/=a&lt;/=0.8, 0&lt;/=b&lt;/=0.2, 0&lt;/=c&lt;/=0.2, 1.5&lt;/=m&lt;/=3.5, 0.5&lt;/=n&lt;/=1.5. 1x10-5&lt;/=x&lt;/=1x10-1, and 1x10-5&lt;/=y&lt;/=1x10-1, and which contains a halogen element such as F, Cl, Br or I in an amount within range of from 1x10-5 to 1x10-1 gxatm/mol of the host material.

TECHNICAL FIELD

The present invention relates to an europium-activated silicate typephosphorescent phosphor which is excellent in weather resistance, has along afterglow characteristic and exhibits blue to green emission underexcitation with ultraviolet rays and/or visible light rays, and which isuseful as a light source or a display in a dark place such as indoor oroutdoor or in water.

BACKGROUND ART

A phosphorescent phosphor is a phosphor which continues to emitfluorescence even after termination of excitation after some excitationis imparted to the phosphor to emit fluorescence. For a phosphorescentphosphor, along with diversification and high functionalization ofdisplay, multi-coloring, long afterglow and improved weather resistanceof a phosphorescent phosphor are desired. With conventionalphosphorescent phosphors, the types of colors of the fluorescence andafterglow were limited, the weather resistance was poor, and theafterglow time was short.

As a blue-emitting phosphorescent phosphor, a (Ca,Sr)S:Bi phosphor isknown. As a yellowish green-emitting phosphorescent phosphor, a ZnS:Cuphosphor is known, and as a red-emitting phosphorescent phosphor, a(Zn,Cd)S:Cu phosphor is known.

However, the above-mentioned (Ca,Sr)S:Bi phosphor is not practicallyused at present, since the chemical stability of the host material isextremely poor, and the luminance and afterglow characteristics areinadequate. On the other hand, the (Zn,Cd)S:Cu phosphor is notpractically used at present, since Cd which is a toxic substance,occupies almost a half of the host material, and the luminance andafterglow characteristics are not satisfactory. ZnS:Cu is alsosusceptible to decomposition by ultraviolet rays in the presence ofmoisture and is likely to be blackened, and the afterglowcharacteristics are also unsatisfactory, but it is inexpensive and isused mostly for face plates of clocks or for indoor use such asemergency escape signs.

DISCLOSURE OF THE INVENTION

The present invention is to overcome the above drawbacks and to providea phosphorescent phosphor which has a long afterglow characteristic andblue to green emission and which is further chemically stable andexcellent in weather resistance.

Namely, the present invention is a phosphorescent phosphor which has thefollowing construction and which exhibits blue to green emission.

(1) In an Eu-activated silicate phosphorescent phosphor, aphosphorescent phosphor represented by a compositional formulam(Sr_(1-a) M¹ _(a))O.n(Mg_(1-b) M² _(b))O.2(Si_(1-c) Ge_(c))O₂ : Eu_(x)Ln_(y), wherein M¹ is at least one element selected from Ca and Ba, M²is at least one element selected from Be, Zn and Cd, and the coactivatorLn is at least one element selected from Sc, Y, La, Ce, Pr, Nd, Sm, Gd,Tb, Dy, Ho, Er, Tm, Yb, Lu, B, Al, Ga, In, Tl, Sb, Bi, As, P, Sn, Pb,Ti, Zr, Hf, V, Nb, Ta, Mo, W, Cr and Mn, and wherein a, b, c, m, n, xand y are within the following ranges, and said phosphor contains atleast one halogen element selected from F, Cl, Br and I in an amountwithin a range of from 1×10⁻⁵ to 1×10⁻¹ g·atm/mol of the host material:

0≦a≦0.8

0≦b≦0.2

0≦c≦0.2

1.5≦m≦3.5

0.5≦n≦1.5

1×10⁻⁵ ≦x≦1×10⁻¹

1×10⁻⁵ ≦y≦1×10⁻¹.

(2) The phosphorescent phosphor according to the above (1), wherein theabove value m satisfies a condition represented by 1.7≦m≦3.3.

(3) The phosphorescent phosphor according to the above (1) or (2),wherein the above coactivator Ln is at least one element selected fromDy, Nd, Tm, Sn, In and Bi.

(4) The fluorescent phosphor according to any one of the above (1) to(3), which exhibits thermoluminescence at a temperature of at least roomtemperature, when heated after excitation with ultraviolet rays and/orvisible light rays within a range of from 140 to 450 nm.

The present inventors have conducted a study primarily on a phosphorhost material of (Sr,M¹)O--(Mg,M²) O--(Si,Ge)O₂ type (M¹ =at least oneof Ca and Ba, and M² =at least one of Be, Zn and Cd), whereby they havefound that a phosphor host material suitable for a long afterglowcharacteristic is present in the compositional region shown by thehatched lines in FIG. 1.

Namely, a phosphor represented by the compositional formulam(Sr_(1-a),M¹ _(a))O.n(Mg_(1-b),M² _(b))O.2(Si_(1-c),Ge.sub.c)O₂,wherein m and n are within ranges of 1.5≦m≦3.5, and 0.5≦n≦1.5, issuitable.

And, in the present invention, the above phosphor host material isactivated with Eu and at the same time, co-activated with Ln (at leastone element selected from Sc, Y, La, Ce, Pr, Nd, Sm, Gd, Tb, Dy, Ho, Er,Tm, Yb, Lu, B, Al, Ga, In, Tl, Sb, Bi, As, P, Sn, Pb, Ti, Zr, Hf, V, Nb,Ta, Mo, W, Cr and Mn), and a halog en element (at least one elementselected from F, Cl, Br and I) is incorporated, whereby it has beensuccessful to optimize the luminescence center (Eu) and the incorporatedelements, and it has been successful to obtain a blue to green-emittingphosphorescent phosphor which has a very long afterglow characteristicand which is chemically stable and excellent in weather resistance.Among the above co-activators Ln, Dy, Nd, Tm, Sn, In and Bi areparticularly excellent.

In the compositional formula of the present invention, the substitutionamount a of Sr is suitably within a range of 0≦a≦0.8, preferably0≦a≦0.4. If it exceeds 0.8, the effect of improving the afterglowcharacteristic tends to be small. The substitution amount b of M²element is suitably within a range of 0≦b≦0.2, preferably 0≦b≦0.1. If itexceeds 0.2, the effect of improving the afterglow characteristic tendsto be small. The amount C of Ge substituted for Si is suitably within arange of 0≦c≦0.2, preferably 0≦c≦0.1. If it exceeds 0.2, the effect ofimproving the afterglow characteristic tends to be small, and theluminance also tends to decrease.

Further, the above m and n values determining the compositional ratio ofm(Sr_(1-a),M¹ _(a))O, n(Mg_(1-b),M² _(b))O and 2(Si_(1-c),Ge_(c))O₂, ascomponents constituting the host material of the phosphor, are suitablywithin ranges of 1.5≦m≦3.5 and 0.5≦n≦1.5, preferably 1.7≦m≦3.3 and0.7≦n≦1.3. If they depart from such ranges, a compound other than thedesired compound will be formed, or the starting material oxides willremain, whereby the luminance will decrease.

The incorporated amount x (g·atm) of the activator Eu is suitably withina range of 1×10⁻⁵ ≦x≦1×10¹, preferably 1×10⁻⁴ ≦x≦5×10⁻². If it is lessthan 1×10⁻⁵, the numbers of the luminescence center tend to diminish,and the desired luminance can not be obtained. Further, if it exceeds1×10⁻¹, concentration quenching takes place, whereby the luminancedecreases, and the afterglow characteristic decreases.

The incorporated amount y (g·atm) of the co-activator element Ln issuitably within a range of 1×10⁻⁵ ≦y≦1×10⁻¹, preferably 1×10⁻⁴≦y≦5×10⁻². If it is less than 1×10⁻⁵, no effect for the afterglowcharacteristic tends to be obtained, and if it exceeds 1×10⁻¹, theco-activator element undergoes light emission, whereby an emission in arange of blue to green can not be obtained.

The halogen element incorporated to the phosphor of the presentinvention serves partially as a flux for crystal growth and fordiffusion of the luminescence center and the co-activator element Ln andimproves the luminance and the afterglow characteristic. Theincorporated amount z(g·atm) of the halogen element is suitably 1×10⁻⁵≦z≦1×10⁻¹, preferably 1× ⁴ ≦z≦1×10² as a value analyzed after thewashing treatment, etc. If it exceeds 1×10⁻¹, the phosphor tends tosinter, whereby treatment into a powder tends to be difficult, and if itis less than 1×10⁻⁵, a drawback such as a decrease in the afterglow andspontaneous emission luminance, tends to result.

And, the phosphorescent phosphor of the present invention exhibitsthermoluminescence at a temperature fat least room temperature, when thephosphor is heated after excitation with ultraviolet rays and/or visiblelight rays within a range of from 140 to 450 nm.

The phosphorescent phosphor of the present invention is synthesized asfollows.

With respect to the materials for the phosphor, the hostmaterial-constituting elements Sr, M¹ (M¹ =at least one of Ca and Ba),Mg, M² (M² =Be, Zn, Cd), Si and Ge, and activator Eu and co-activatorLn, are used in the form of the respective oxides or in the form ofsalts such as carbonates, nitrates or chlorides which can readily beconverted to oxides by baking. Further, the halogen elements are used inthe form of ammonium salts, alkali metal salts or halogenated compoundsof the above-mentioned constituting elements (the hostmaterial-constituting elements, activator element Eu or co-activatorelement Ln). And, they are sampled so that the composition will bestoichiometrically within the above compositional formula and thoroughlymixed in a wet system or in a dry system. Rare earth materials may bemixed to one another by co-precipitation. This mixture is filled in aheat resistant container such as an alumina crucible and baked at leastonce at a temperature of from 800 to 1400° C. for from 1 to 12 hours ina reducing atmosphere of hydrogen-containing neutral gas or in areducing atmosphere consisting of carbon element-containing gas, e.g.CO_(x) gas, CS₂ gas etc. When baking is carried out in a plurality oftimes, the final baking step is carried out necessarily in a reducingatmosphere. This baked product is pulverized and then subjected towashing with a weak mineral acid, washing with water, drying, sieving,etc., to obtain the phosphorescent phosphor of the present invention.

FIG. 2 is an X-ray diffraction pattern, whereby the crystal structure ofthe phosphorescent phosphor Sr₁.995 Mgsi₂ O₇ :Eu₀.005, Dy₀.025, Cl₀.025synthesized in Example 1, was confirmed. FIG. 3 is an X-ray diffractionpattern whereby the crystal structure of the phosphorescent phosphorSr₂.97 MgSi₂ O₈ :Eu₀.03, Dy₀.025, Cl₀.025 synthesized in Example 2, wasconfirmed. Even when a part of Sr, Mg or Si in these phosphorcompositions, was substituted by other elements within the range definedin the Claims, substantially the same results were obtained.

FIG. 4 shows emission spectra, under excitation with ultraviolet rays of365 nm, of the phosphorescent phosphor (curve a) of Example 1, thephosphorescent phosphor Sr₁.195 Ca₀.8 MgSi₂ O₇ :Eu₀.005,Dy₀.025,Br₀.025(curve b), synthesized in Example 3 and the phosphorescent phosphorSr₀.995 BaMgSi₂ O₇ :Eu₀.005,Dy₀.025,Br₀.025 (curve b) synthesized inExample 5, and the respective emission peak wavelengths were 470 nm, 500nm and 450 nm. Further, FIG. 5 shows emission spectra, under excitationwith ultraviolet rays of 365 nm, of the phosphorescent phosphor (curvea) of Example 2, the phosphorescent phosphor Sr₂.07 Ca₀.9 Mgsi₂ O₈:Eu₀.03,Dy₀.025,Cl₀.025 (curve b) synthesized in Example 4 and thephosphorescent phosphor Sr₂.375 Ba₀.6 MgSi₂ O₈ :Eu₀.025 Dy₀.3.Br₀.015(curve c) synthesized in Example 6, and the respective emission peakwavelengths were 460 nm, 471 nm and 450 nm. Even if a part of thesephosphor compositions, was substituted by other elements within therange defined in the Claims, substantially the same results wereobtained.

FIG. 6 is one wherein using the phosphorescent phosphor of Example 1,the region of the excited spectrum was measured and shown. FIG. 7 is onewherein using the phosphorescent phosphor of Example 2, the region ofthe excited spectrum was measured and shown. In the measurement of theregion of the excited spectrum, the intensity of 460 nm (output light)was plotted when the exciting wavelength of light irradiated to thesample, was varied while the spectrum wavelength on the output side ofthe spectrophotometer, is fixed at 460 nm, whereby the ordinaterepresents the relative emission intensity of 460 nm, and the abscissarepresents the wavelength of the scanning exciting light. Even if a partof this phosphor composition was substituted by other elements withinthe range as defined in the Claims, substantially the same results wereobtained.

In FIG. 8, the phosphorescent phosphor of Example 1 (the emissionspectrum peak wavelength: 470 nm), the phosphorescent phosphor ofExample 3 (the emission spectrum peak wavelength: 500 nm), thephosphorescent phosphor of Example 5 (the emission spectrum peakwavelength: 450 nm), the phosphorescent phosphor of Comparative Example1 (Sr₁.995 MgSi₂ O₇ :Eu₀.005, the emission spectrum peak wavelength: 470nm) and the phosphorescent phosphor of Comparative Example 3 (ZnS:Cu,the emission spectrum peak wavelength: 516 nm) were irradiated with 300lux for 30 minutes by means of a day light color fluorescent lamp, andthe afterglow characteristics upon expiration of 2 minutes aftertermination of the irradiation, were measured. Further, in FIG. 9, thephosphorescent phosphor of Example 2 (the emission spectrum peakwavelength: 460 nm), the phosphorescent phosphor of Example 4 (theemission spectrum peak wavelength: 471 nm), the phosphorescent phosphorof Example 6 (the emission spectrum peak wavelength: 450 nm), thephosphorescent phosphor of Comparative Example 2 (Sr₂.97 MgSi₂ O₈:Eu₀.03, the emission spectrum peak wavelength: 460 nm) and thephosphorescent phosphor of Comparative Example 3 (ZnS:Cu, the emissionspectrum peak wavelength: 516 nm) were irradiated with 300 lux for 30minutes by means of a day light color fluorescent lamp, and theafterglow characteristics upon expiration of 2 minutes after terminationof irradiation, were measured. In each case, the measuring method wassuch that, as described above, the sample was irradiated with a 30 W daylight color fluorescent lamp, and the afterglow of the phosphor afterswitching off the lamp, was determined by measuring the luminance of theafterglow by a luminance meter provided with a filter adjusted toluminosity curve.

As is evident from FIGS. 8 and 9, the phosphorescent phosphor having anemission spectrum peak wavelength of 470 nm of Example 1 has anextremely remarkable afterglow characteristic as compared withComparative Example 1. Further, it is evident that the phosphorescentphosphor having an emission spectrum peak wavelength of 460 nm ofExample 2 has an extremely remarkable afterglow characteristic ascompared with Comparative Example 2. Further, it is evident that thephosphorescent phosphors of Examples 4 and 6 have excellent afterglowcharacteristics as compared with the ZnS:Cu yellowish green-emittingphosphor of Comparative Example 3 which corresponds to a commercialproduct, although the emission colors are different. Furthermore, therespective phosphorescent phosphors of Examples 3, 4, 5 and 6 also haveexcellent afterglow characteristics as compared with the ZnS:Cuyellowish green-emitting phosphor of Comparative Example 3 whichcorresponds to a commercial product, although the emission colors aredifferent.

FIG. 10 is a graph showing the results, when the respectivephosphorescent phosphors of Examples 1, 3 and 5 were irradiated with 300lux for 15 seconds by a day light color fluorescent lamp, and thethermoluminescence characteristic (glow curve) upon expiration of 1minute after termination of irradiation was measured at a temperatureraising rate of about 8 to 10° C./sec by means of TLD reader (KYOKKOTLD-1300 improved type), manufactured by Kasei Optonix, Ltd. FIG. 11 isa graph showing the results, when the phosphorescent phosphors ofExamples 2, 4 and 6 were irradiated with 300 lux for 15 seconds by a daylight color fluorescent lamp as described above, and thethermoluminescence characteristic (glow curve) upon expiration of 1minute after termination of irradiation, was measured by TLD reader(KYOKKO TLD-1300 improved type) manufactured by Kasei Optonix, Ltd. Asis evident from curves a to c in FIG. 10 and curves a to c in FIG. 11,the phosphorescent phosphors of Examples 1 to 6 exhibitthermoluminescence when heated at the above-mentionedtemperature-raising speed within a temperature range of at least roomtemperature.

The phosphorescent phosphor of the present invention exhibits a veryhigh luminance afterglow characteristic as described above and isexcellent in weather resistance and chemically stable, and even whencompared with the conventional ZnS type phosphorescent phosphors, itmakes application possible not only to indoors but also to a wide rangeof applications outdoors. For example, it may be coated on the surfacesof various articles, or it may be mixed in plastics, rubbers, polyvinylchlorides, synthetic resins or glass and may be applied widely in theform of molded products or fluorescent films, for example, for varioussigns for traffic safety (such as traffic armbands, traffic controlgloves, reflectors of vehicles, reflector flags, signals, road signs,emergency ropes, footgears, safety umbrellas, sticks for blind persons,stickers, knapsacks, raincoats or safety covers), indicators (such astelephone dial covers, switches, slip prevention of stair case, escapeguide signals, tires, mannequins, fire extinguishers, keys, doors,fluorescent lamps or display tapes), ornaments (such as artificialflowers, accessories or interior plates), various leisure articles (suchas floats for fishing, toys, golf balls, ropes, kites, artificial treesor puzzles), clocks (such as face plates, hands or scales), officearticles and office appliances (such as writing means, cardboards,scales, marker pens, seals, liquid crystal back lights, solar cells,calculators, printers or inks), educational articles and appliances(such as constellation plates, planet models, transparency, keyedinstruments or maps) and building materials (such as concrete, guardrails, scales for construction work, scaffoldings for manholes, tiles,decorative laminated sheets, measuring apparatus or tape measures).

Especially when the phosphorescent phosphor of the present invention isused alone or as a blue to bluish green-emitting component phosphor fora high color rendering fluorescent lamp, and this is coated on a tubularwall of the fluorescent lamp and used as a fluorescent film for thefluorescent lamp, it continues to emit fluorescence with high luminancefor a long period of time even when the lamp is suddenly off due to e.g.power breakdown, and thus it is useful also as an emergency fluorescentlamp.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a graph showing a ternary state diagram of a(Sr,M¹)O--(Mg,M²)O--(Si,Ge)O₂ type oxide which is the host material ofthe phosphorescent phosphor of the present invention.

FIG. 2 is an X-ray diffraction pattern whereby the crystal structure ofthe phosphorescent phosphor synthesized in Example 1 was confirmed.

FIG. 3 is an X-ray diffraction pattern whereby the crystal structure ofthe phosphorescent phosphor synthesized in Example 2 was confirmed.

FIG. 4 is a graph showing emission spectra when the phosphorescentphosphors synthesized in Examples 1, 3 and 5 were excited withultraviolet rays of 365 nm.

FIG. 5 is a graph showing emission spectra when the phosphorescentphosphors synthesized in Examples 2, 4 and 6 were excited withultraviolet rays of 365 nm.

FIG. 6 is a graph showing the excitation spectrum at each emissionspectrum peak of the phosphorescent phosphor of Example 1.

FIG. 7 is a graph showing the excitation spectrum at each emissionspectrum peak of the phosphorescent phosphor of Example 2.

FIG. 8 is a graph wherein the afterglow characteristics were comparedamong the blue to green-emitting phosphorescent phosphors of Examples 1,3 and 5 and Comparative Example 1 and the yellowish green-emittingphosphorescent phosphor of Comparative Example 3.

FIG. 9 is a graph wherein the afterglow characteristics were comparedamong the blue to green-emitting phosphorescent phosphors of Examples 2,4 and 6 and Comparative Example 2 and the yellowish green-emittingphosphorescent phosphor of Comparative Example 3.

FIG. 10 is a graph showing the thermoluminescence characteristics (glowcurves) of the phosphorescent phosphors of Examples 1, 3 and 5.

FIG. 11 is a graph showing the thermoluminescence characteristics (glowcurves) of the phosphorescent phosphors of Examples 2, 4 and 6.

BEST MODE FOR CARRYING OUT THE INVENTION

The present invention will be described in further detail with referenceto the following Examples, but it is by no means restricted by thefollowing Examples unless it exceeds the gist thereof.

EXAMPLE

    ______________________________________           SrCO.sub.3    29.5   g           MgO           4.0    g           SiO.sub.2     12.0   g           Eu.sub.2 O.sub.3                         0.09   g           Dy.sub.2 O.sub.3                         0.47   g           NH.sub.4 Cl   2.3    g    ______________________________________

The above starting materials were thoroughly mixed, packed into analumina crucible and baked at 115° C. for 2 hours in a reducingatmosphere comprising 98% of nitrogen and 2% of hydrogen, by means of anelectric furnace. The obtained baked product was pulverized andsubjected to washing with water, drying and sieving to obtain aphosphorescent phosphor.

This phosphor had a composition of Sr₁.995 MgSi₂ O₇ :Eu₀.005, Dy₀.025Cl₀.025 and showed an X-ray diffraction pattern of FIG. 2, and theemission spectrum under excitation with ultraviolet rays of 365 nm wasas shown in FIG. 4 (curve a), whereby its emission peak wavelength had ablue-emitting phosphorescence of 470 nm. Further, the excitationspectrum was found to extend to a visible region, as shown in FIG. 6.The afterglow characteristic showed a long afterglow as shown in FIG. 8(curve a). Further, the glow curve was as shown in FIG. 10. Furthermore,the emission peak wavelength of the phosphor, the afterglowcharacteristic (the emission intensity ratio of the emission intensitiesupon expiration of 2 minutes and 60 minutes after termination ofirradiation as compared with a ZnS:Cu yellowish green-emittingphosphorescent phosphor being 100%) and the peak temperature value ofthe glow curve, are shown in Table 1.

EXAMPLE

    ______________________________________           SrCO.sub.3    43.8   g           MgO           4.0    g           SiO.sub.2     12.0   g           Eu.sub.2 O.sub.3                         0.53   g           Dy.sub.2 O.sub.3                         0.47   g           NH.sub.4 Cl   2.3    g    ______________________________________

The above starting materials were thoroughly mixed, packed into analumina crucible and baked at 1150° C. for 2 hours in a reducingatmosphere comprising 98% of nitrogen and 2% of hydrogen by means of anelectric furnace. The obtained baked product was pulverized andsubjected to washing with water, drying and sieving to obtain aphosphorescent phosphor.

This phosphor had a composition of Sr₂.97 Mgsi₂ O₈ :Eu₀.03 Dy₀.025Cl₀.025 and showed an X-ray diffraction pattern of FIG. 3, and theemission spectrum under excitation with ultraviolet rays of 365 nm wasas shown in FIG. 5 (curve a), whereby its emission peak wavelength had ablue-emitting phosphorescence of 460 Further, the excitation spectrumwas found to extend to a visible region, as shown in FIG. 7. Theafterglow characteristic showed a long afterglow, as shown in FIG. 9(curve a). Further, the glow curve was as shown in FIG. 11. Furthermore,the emission peak wavelength of the phosphor, the afterglowcharacteristic (the emission intensity ratio of the emission intensitiesupon expiration of 2 minutes and 60 minutes after termination ofirradiation, as compared with a ZnS:Cu yellowish green-emittingphosphorescent phosphor being 100%) and the peak temperature value ofthe glow curve, are shown in Table

EXAMPLE

    ______________________________________           SrCO.sub.3    17.6   g           CaCO.sub.3    8.0    g           MgO           4.0    g           SiO.sub.2     12.0   g           Eu.sub.2 O.sub.3                         0.09   g           Dy.sub.2 O.sub.3                         0.47   g           NH.sub.4 Br   3.3    g    ______________________________________

The above starting materials were thoroughly mixed, packed into analumina crucible and baked at 1200° C. for 2 hours in a carbon-reducingatmosphere by means of an electric furnace. The obtained baked productwas pulverized and subjected to washing with water, drying and sievingto obtain a phosphorescent phosphor.

This phosphor had a composition of Sr₁.195 Ca₀.8 Mgsi₂ O₇ Eu₀.005Dy₀.025,Br₀.025, and the emission spectrum under excitation withultraviolet rays of 365 nm was as shown in FIG. 4 (curve b), whereby itspeak wavelength had a green-emitting phosphorescence of 500 nm. Further,the afterglow characteristic showed a long afterglow, as shown in FIG. 8(curve b). Further, the glow curve was as shown in FIG. 10 (curve b).Furthermore, the emission peak wavelength of the phosphor, the afterglowcharacteristic (the emission intensity ratio of the emission intensitiesupon expiration of 2 minutes and 60 minutes after termination ofirradiation, as compared with a ZnS:Cu yellowish green-emittingphosphorescent phosphor being 100%) and the glow peak temperature, areshown in Table 1.

EXAMPLE

    ______________________________________           SrCO.sub.3    30.6   g           CaCO.sub.3    9.1    g           MgO           4.0    g           SiO.sub.2     12.0   g           Eu.sub.2 O.sub.3                         0.52   g           Dy.sub.2 O.sub.3                         0.47   g           NH.sub.4 Cl   2.6    g    ______________________________________

The above starting materials were thoroughly mixed, packed into analumina crucible and baked at 1200° C. for 2 hours in a reducingatmosphere consisting of carbon element-containing gas, e.g. Co_(x) gas,CS₂ gas etc. The obtained baked product was pulverized and subjected towashing with water, drying and sieving to obtain a phosphorescentphosphor.

This phosphor had a composition of Sr₂.07 Ca₀.9 Mgsi₂ O₈ :Eu₀.03 Dy₀.025Cl₀.02, and the emission spectrum under excitation with ultraviolet raysof 365 nm was as shown in FIG. 5 (curve b), whereby its peak had abluish green-emitting phosphorescence of 471 nm. Further, the afterglowcharacteristic showed a long afterglow, as shown in FIG. 9 (curve b).Further, the glow curve was as shown in FIG. 11 (curve b). Furthermore,the emission peak wavelength of the phosphor, the afterglowcharacteristic (the emission intensity ratio of the emission intensitiesupon expiration of 2 minutes and 60 minutes after termination ofirradiation, as compared with a ZnS:Cu yellowish green-emittingphosphorescent phosphor being 100%) and the glow peak temperature value,are shown in Table 1.

EXAMPLE

    ______________________________________           SrCO.sub.3    14.7   g           BaCO.sub.3    19.7   g           MgO           4.0    g           SiO.sub.2     12.0   g           Eu.sub.2 O.sub.3                         0.09   g           Dy.sub.2 O.sub.3                         0.47   g           NH.sub.4 Br   2.68   g    ______________________________________

The above starting materials were thoroughly mixed, packed into analumina crucible and baked at 1200° C. for 3 hours in a reducingatmosphere comprising 97% of nitrogen and 3% of hydrogen, by means of anelectric furnace. The obtained baked product was pulverized andsubjected to washing with water, drying and sieving to obtain aphosphorescent phosphor.

This phosphor had a composition of Sr₀.995 Ba₁.0 MgSi₂ O₇ :Eu₀.005,Dy₀.025, Br₀.25, and the emission spectrum under excitation withultraviolet rays of 365 nm was as shown in FIG. 4 (curve c), whereby itspeak had a bluish green-emitting phosphorescence of 450 nm. Further, theafterglow characteristic showed a long afterglow, as shown in FIG. 8(curve c). Further, the glow curve was as shown in FIG. 10 (curve c).Furthermore, the emission peak value of the phosphor, the afterglowcharacteristic (the emission intensity ratio of the emission intensitiesupon expiration of 2 minutes and 60 minutes after termination ofirradiation, as compared with a ZnS:Cu yellowish green-emittingphosphorescent phosphor being 100%) and the peak temperature value ofthe glow curve, are shown in Table 1.

EXAMPLE

    ______________________________________           SrCO.sub.3    35.1   g           BaCO.sub.3    11.8   g           MgO           4.0    g           SiO.sub.2     12.0   g           Eu.sub.2 O.sub.3                         0.44   g           Dy.sub.2 O.sub.3                         0.56   g           NH.sub.4 Br   1.6    g    ______________________________________

The above starting materials were thoroughly mixed, packed into analumina crucible and baked at 1200° C. for 3 hours in a reducingatmosphere comprising 97% of nitrogen and 3% of hydrogen, by means of anelectric furnace. The obtained baked product was pulverized andsubjected to washing with water, drying and sieving to obtain aphosphorescent phosphor.

This phosphor had a composition of Sr₂.35 Ba₀.6 MgSi₂ O₈ :Eu₀.025 Dy₀.3Br₀.015, and the emission spectrum under excitation with ultravioletrays of 365 nm was as shown in FIG. 5 (curve c), whereby its peak had abluish-emitting phosphorescence of 450 nm. Further, the afterglowcharacteristic showed a long afterglow, as shown in FIG. 9 (curve c).Further, the glow curve was as shown in FIG. 11 (curve c). Furthermore,the emission peak value of the phosphor, the afterglow characteristic(the emission intensity ratio of the emission intensities uponexpiration of 2 minutes and 60 minutes after termination of irradiation,as compared with a ZnS:Cu yellowish green-emitting phosphorescentphosphor being 100%) and the peak temperature value of the glow curve,are shown in Table 1.

EXAMPLES 7 to 22

In the same manner as in Example 1, the hosphorescent phosphors ofExamples 7 to 22 having compositions as disclosed in Tables 1 and 2,were obtained. The emission peak values of the phosphors of Examples 7to 22, the afterglow characteristics (the emission intensity ratios ofthe emission intensities upon expiration of 2 minutes and 60 minutesafter termination of irradiation, as compared with a ZnS:Cu yellowishgreen-emitting phosphorescent phosphor being 100%) and the glow peaktemperature values are shown in Tables 1 and 2.

EXAMPLES 23 to 37

In the same manner as in Example 2, phosphorescent phosphors of Examples23 to 37 having the compositions as disclosed in Table 4, were obtained.The emission peak values of the phosphors of Examples 23 to 37, theafterglow characteristics (the emission intensity ratios of the emissionintensities upon expiration of 2 minutes and 60 minutes aftertermination of irradiation, as compared with a ZnS:Cu yellowishgreen-emitting phosphorescent phosphor being 100%) and the glow peaktemperature values, were shown in Tables 3 and 4.

COMPARATIVE EXAMPLES 1 and 3

A Sr₁.995 MgSi₂ O₇ :Eu₀.005 phosphorescent phosphor of ComparativeExample 1 was obtained in the same manner as in Example 1 except thatincorporation of the coactivator element Ln and the halogen element wasomitted.

COMPARATIVE EXAMPLE 2

A Sr₂.97 MgSi₂ O₈ :Eu₀.03 phosphorescent phosphor of Comparative Example2 was obtained in the same manner as in Example 2 except thatincorporation of the coactivator element Ln and the halogen element wasomitted.

COMPARATIVE EXAMPLE 3

A ZnS:Cu yellowish green-emitting phosphorescent phosphor (LC-G1)manufactured by Kasei Optonix, Ltd. was used as a reference sample, andthis was used as a phosphor of Comparative Example 3.

The emission peak wavelengths of the respective phosphors of theseComparative Examples 1 to 3, the afterglow characteristics (the emissionintensity ratios of the emission intensities upon expiration of 2minutes and 60 minutes after termination of irradiation, as comparedwith a ZnS:Cu yellowish green phosphorescent phosphor being 100%) andthe peak values of the glow curves, are shown in Table 4.

INDUSTRIAL APPLICABILITY

By adopting the above-described construction, the present inventionmakes it possible to present for the first time a blue to green-emittingphosphorescent phosphor which is chemically stable and which exhibitshigh luminance and a far longer afterglow as compared with acommercially available ZnS type yellowish green-emitting phosphorescentphosphor, and thus substantially contributes to multi-coloring anddiversification of display.

                                      TABLE 1    __________________________________________________________________________                                 Afterglow                                 characteristics                            Emission                                 5 minutes                                      60 minutes                                            Glow peak    Chemical compositional formula                            peak (nm)                                 later                                      later (° C.)    __________________________________________________________________________    Ex. 1        Sr.sub.1.995 MgSi.sub.2 O.sub.7 :Eu.sub.0.005 Dy.sub.0.025 Cl.sub.0.02        5                   470  480  1540  90    Ex. 2        Sr.sub.2.97 MgSi.sub.2 O.sub.8 :Eu.sub.0.03 Dy.sub.0.025 Cl.sub.0.025                            460  250  800   90    Ex. 3        Sr.sub.1.995 Ca.sub.0.8 MgSi.sub.2 O.sub.7 :Eu.sub.0.005 Dy.sub.0.025        Br.sub.0.025        500  180  250   70    Ex. 4        Sr.sub.2.07 Ca.sub.0.9 MgSi.sub.2 O.sub.8 :Eu.sub.0.03 Dy.sub.0.025        Cl.sub.0.02         471  155  350   85    Ex. 5        Sr.sub.1.995 Ba.sub.1.0 MgSi.sub.2 O.sub.7 :Eu.sub.0.005 Dy.sub.0.025        Br.sub.0.025        450  195  440   100    Ex. 6        Sr.sub.2.375 Ba.sub.0.6 MgSi.sub.2 O.sub.8 :Eu.sub.0.025 Dy.sub.0.03        Br.sub.0.015        450  150  200   80    Ex. 7        Sr.sub.1.995 MgSi.sub.2 O.sub.7 :Eu.sub.0.005 Dy.sub.0.025                            470  60   180   85    Ex. 8        Sr.sub.1.995 MgSi.sub.2 O.sub.7 :Eu.sub.0.005 Dy.sub.0.025 Cl.sub.0.05                            470  870  2530  95    Ex. 9        Sr.sub.1.995 MgSi.sub.2 O.sub.7 :Eu.sub.0.005 Dy.sub.0.025 Br.sub.0.03                            470  705  1830  95    Ex. 10        Sr.sub.1.97 MgSi.sub.2 O.sub.7 :Eu.sub.0.03 Dy.sub.0.025 F.sub.0.01                            470  195  280   80    __________________________________________________________________________

                                      TABLE 2    __________________________________________________________________________                                 Afterglow                                 characteristics                            Emission                                 5 minutes                                      60 minutes                                            Glow peak    Chemical compositional formula                            peak (nm)                                 later                                      later (° C.)    __________________________________________________________________________    Ex. 11        Sr.sub.1.97 MgSi.sub.2 O.sub.7 :Eu.sub.0.03 Dy.sub.0.025 Cl.sub.0.025                            470  450  990   90    Ex. 12        Sr.sub.1.97 MgSi.sub.2 O.sub.7 :Eu.sub.0.03 Dy.sub.0.02 Cl.sub.0.025                            470  330  710   80    Ex. 13        Sr.sub.1.995 MgSi.sub.2 O.sub.7 :Eu.sub.0.005 Nd.sub.0.025 Br.sub.0.02        5                   470  75   210   70    Ex. 14        Sr.sub.1.995 MgSi.sub.2 O.sub.7 :Eu.sub.0.005 Tm.sub.0.025 Br.sub.0.02        5                   470  70   200   80    Ex. 15        Sr.sub.1.995 MgSi.sub.2 O.sub.7 :Eu.sub.0.005 In.sub.0.025 Br.sub.0.02        5                   470  45   120   75    Ex. 16        Sr.sub.1.995 MgSi.sub.2 O.sub.7 :Eu.sub.0.005 Bi.sub.0.025 Br.sub.0.02        5                   470  40   110   70    Ex. 17        Sr.sub.1.995 MgSi.sub.2 O.sub.7 :Eu.sub.0.005 Sn.sub.0.025 Br.sub.0.02        5                   470  45   110   80    Ex. 18        Sr.sub.0.395 Ba.sub.1.8 MgSi.sub.2 O.sub.7 :Eu.sub.0.005 Dy.sub.0.025        Br.sub.0.025        470  45   230   90    Ex. 19        Sr.sub.1.995 Mg.sub.0.9 Zn.sub.0.1 Si.sub.2 O.sub.7 :Eu.sub.0.005        Dy.sub.0.025 Cl.sub.0.025                            470  525  1330  80    Ex. 20        Sr.sub.1.995 MgSi.sub.1.96 Ge.sub.0.04 O.sub.7 :Eu.sub.0.005 Dy.sub.0.        025 Cl.sub.0.025    470  330  1200  80    Ex. 21        Sr.sub.1.995 Mg.sub.0.97 Cd.sub.0.03 Si.sub.2 O.sub.7 :Eu.sub.0.005        Dy.sub.0.025 Cl.sub.0.03                             470 420  920   75    Ex. 22        Sr.sub.1.995 Mg.sub.0.97 Be.sub.0.03 Si.sub.2 O.sub.7 :Eu.sub.0.005        Dy.sub.0.025 Cl.sub.0.025                            470  395  900   80    __________________________________________________________________________

                                      TABLE 3    __________________________________________________________________________                                Afterglow                                characteristics                           Emission                                5 minutes                                     60 minutes                                           Glow peak    Chemical compositional formula                           peak (nm)                                later                                     later (° C.)    __________________________________________________________________________    Ex. 23        Sr.sub.2.97 MgSi.sub.2 O.sub.8 :Eu.sub.0.03 Dy.sub.0.025                           460  40   150   80    Ex. 24        Sr.sub.2.97 MgSi.sub.2 O.sub.8 :Eu.sub.0.03 Dy.sub.0.025 Cl.sub.0.05                           460  300  800   90    Ex. 25        Sr.sub.2.97 MgSi.sub.2 O.sub.8 :Eu.sub.0.03 Dy.sub.0.025 Br.sub.0.03                           460  250  750   95    Ex. 26        Sr.sub.2.97 MgSi.sub.2 O.sub.8 :Eu.sub.0.03 Dy.sub.0.025 F.sub.0.025                           460  300  750   85    Ex. 27        Sr.sub.2.97 MgSi.sub.2 O.sub.8 :Eu.sub.0.05 Dy.sub.0.025 Cl.sub.0.025                           460  280  700   90    Ex. 28        Sr.sub.2.97 MgSi.sub.2 O.sub.8 :Eu.sub.0.05 Dy.sub.0.025 Cl.sub.0.025                           460  250  600   80    Ex. 29        Sr.sub.2.97 MgSi.sub.2 O.sub.8 :Eu.sub.0.03 Nd.sub.0.025 Cl.sub.0.025                           460  230  700   95    Ex. 30        Sr.sub.2.97 MgSi.sub.2 O.sub.8 :Eu.sub.0.03 Tm.sub.0.025 Cl.sub.0.025                           460  75   185   90    Ex. 31        Sr.sub.2.97 Ca.sub.0.9 MgSi.sub.2 O.sub.8 :Eu.sub.0.03 In.sub.0.025        Cl.sub.0.025       460  70   175   95    __________________________________________________________________________

                                      TABLE 4    __________________________________________________________________________                                 Afterglow                                 characteristics                            Emission                                 5 minutes                                      60 minutes                                            Glow peak    Chemical compositional formula                            peak (nm)                                 later                                      later (° C.)    __________________________________________________________________________    Ex. 32        Sr.sub.2.97 MgSi.sub.2 O.sub.8 :Eu.sub.0.03 Bi.sub.0.025 Cl.sub.0.025                            460  50   120   85    Ex. 33        Sr.sub.2.97 MgSi.sub.2 O.sub.8 :Eu.sub.0.03 Sn.sub.0.025 Cl.sub.0.025                            460  85   210   90    Ex. 34        Sr.sub.2.97 Mg.sub.0.9 Zn.sub.0.1 Si.sub.2 O.sub.8 :Eu.sub.0.03        Dy.sub.0.025 Cl.sub.0.025                            460  100  260   90    Ex. 35        Sr.sub.2.97 Mg.sub.0.9 Cd.sub.0.1 Si.sub.2 O.sub.8 :Eu.sub.0.03        Dy.sub.0.025 Cl.sub.0.025                            460  60   150   85    Ex. 26        Sr.sub.2.97 Mg.sub.0.9 Be.sub.0.1 Si.sub.2 O.sub.8 :Eu.sub.0.03        Dy.sub.0.025 Cl.sub.0.025                            460  50   125   90    Ex. 37        Sr.sub.2.97 Mg.sub.1.95 Ge.sub.0.05 Si.sub.2 O.sub.8 :Eu.sub.0.03        Dy.sub.0.025 Cl.sub.0.03                            460  43   115   80    Comp.        Sr.sub.1.995 MgSi.sub.2 O.sub.7 :Eu.sub.0.005                            470  3    0     80    Ex. 1    Comp.        Sr.sub.2.97 MgSi.sub.2 O.sub.8 :Eu.sub.0.03                            460  5    0     90    Ex. 2    Comp.        ZnS:Cu              516  100  100   120    Ex. 3    __________________________________________________________________________

We claim:
 1. A phosphorescent phosphor represented by a compositionalformula m(Sr_(1-a) M¹ _(a))O.n(Mg_(1-b) M² _(b))O.2(Si_(1-c) Ge_(c))O₂Eu_(x) Ln_(y), wherein M¹ is at least one element selected from Ca andBa, M² is at least one element selected from Be, Zn and Cd, and thecoactivator Ln is at least one element selected from Sc, Y, La, Ce, Pr,Nd, Sm, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, B, Al, Ga, In, Tl, Sb, Bi, As,P, Sn, Pb, Ti, Zr, Hf, V, Nb, Ta, Mo, W, Cr and Mn, and wherein a, b, c,m, n, x and y are within the following ranges, and said phosphorcontains at least one halogen element selected from F, Cl, Br and I inan amount within a range of from 1×10⁻⁵ to 1×10⁻¹ g·atm/mol of the hostmaterial:0≦a≦0.8 0≦b≦0.2 0≦c≦0.2 1.5≦m≦3.5 0.5≦n≦1.5 1×10⁻⁵ ≦x≦1×10⁻¹1×10⁻⁵ ≦y≦1×10⁻¹.
 2. The phosphorescent phosphor according to claim 1,wherein the above value m satisfies a condition represented by1.7≦m≦3.3.
 3. The phosphorescent phosphor according to claim 1, whereinthe above coactivator Ln is at least one element selected from Dy, Nd,Tm, Sn, In and Bi.
 4. The fluorescent phosphor according to claim 1,which exhibits thermoluminescence at a temperature of at least roomtemperature, when heated after excitation with ultraviolet rays and/orvisible light rays within a range of from 140 to 450 nm.